Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
  • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
  • B62D5/0481—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
  • B62D5/0484—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures for reaction to failures, e.g. limp home
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D1/00—Steering controls, i.e. means for initiating a change of direction of the vehicle
  • B62D1/02—Steering controls, i.e. means for initiating a change of direction of the vehicle vehicle-mounted
  • B62D1/16—Steering columns
  • B62D1/166—Means changing the transfer ratio between steering wheel and steering gear
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/008—Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
  • B62D5/30—Safety devices, e.g. alternate emergency power supply or transmission means to ensure steering upon failure of the primary steering means

Definitions

• the present invention relates to a method in a steering arrangement for a vehicle, comprising a steering element connected to at least one wheel of the vehicle, with the steering angle of the said wheel of the vehicle being controlled in response to a movement of the steering element according to the preamble to claim 1.
• the invention also relates to a computer program and a computer program product in a steering arrangement for a vehicle according to the preamble to claims 7, 8 and 9.
• the said servo steering comprises for this purpose a hydraulic pump, that is driven by the vehicle's propulsion motor, that pumps hydraulic oil that urges the steering in the direction in which the driver of the vehicle turns the vehicle's steering wheel.
• the ratio between the number of revolutions that the driver must turn the steering wheel between full steering lock positions from right to left is called the "gear ratio" - a high gear ratio thus means that relatively many revolutions of the steering wheel are required between the full lock positions .
• a relatively low gear ratio is normally selected as this means that the steering is more direct and it is more comfortable as the steering wheel needs to be turned less, for example when parking.
• the function of the servo steering is reduced or lost completely for some reason, for example in the event of a breakdown of the hydraulic pump or an engine stoppage, the resistance to turning of the steering wheel will be very high, which makes continued driving of the vehicle difficult.
• a steering wheel is normally used with a relatively large diameter which is easier to turn than a steering wheel with a small diameter in the event of the function of the servo steering being reduced or lost. This results, however, in the disadvantage that the steering feels less direct and that the steering wheel takes up a relatively large amount of the limited space that constitutes the space for the driver.
• servo steering are variants of so-called electrical servo steering, that is where the power from an electric motor is transferred to the steering arrangement in order to make steering of the wheels of the vehicle easier and in this way, as described above, to enable a relatively low gear ratio to be selected in combination with a steering wheel with a relatively small diameter.
• electrical servo steering that is where the power from an electric motor is transferred to the steering arrangement in order to make steering of the wheels of the vehicle easier and in this way, as described above, to enable a relatively low gear ratio to be selected in combination with a steering wheel with a relatively small diameter.
• a first object of the invention is to achieve a method in a steering arrangement for a vehicle that enables a steering wheel with a relatively small diameter to be used in combination with a relatively low gear ratio, even on heavy vehicles such as buses and lorries, without the resistance to turning of the steering wheel being too high, and thereby making continued driving of the vehicle difficult, if the function of the servo steering is reduced or lost completely for some reason.
• This object is achieved by the invention described in claim 1.
• Preferred embodiments of the invention are described in the following claims .
• the invention relates to a method in a steering arrangement for a vehicle, comprising a steering element connected to at least one wheel of the vehicle, with the steering angle of the said wheel of the vehicle being controlled in response to a movement of the steering element, with the function of a servo device connected to the steering arrangement being detected and with the gear ratio between the said movement of the steering element and the steering angle of the wheel of the vehicle being controlled in response to the function of the said servo device.
• servo device makes easier or reduces the force or turning moment that is required in order to achieve a certain movement of the steering element that is required in order to achieve a certain steering angle.
• An additional object of the invention is to compensate for the force that must be applied to the steering element in order to achieve a required steering angle upon the detection of reduced function of the servo device, by the gear ratio being increased by a factor corresponding to the said reduction in function of the servo device, so that the said force is less than a predetermined maximum level.
• the gear ratio is increased by a predetermined factor from a normal ratio to a higher ratio that corresponds to the servo device being completely out of action. Accordingly, a simple device is required for controlling the said gear ratio.
• the gear ratio is increased in steps, from a normal ratio to a higher ratio corresponding to the detected reduction in function of the servo device.
• the said stepwise increase is preferably carried out in three or more steps.
• the gear ratio is varied steplessly, from the said normal ratio to a maximally increased ratio.
• the gear ratio is increased from the said normal ratio to a maximally increased ratio that corresponds to the function of the servo device being lost completely, by a factor in the range 1.2 to 3.5, preferably 1.25 to 2.25.
• the function of the servo device is detected by a pressure sensor that detects the hydraulic pressure at the outlet of the hydraulic pump. Additional or alternative pressure sensors can also be arranged in other places in the hydraulic system in order, in this way, to provide a good indication of the function of the servo device.
• the function of an electrical servo device comprising an electric motor, is detected by the speed and/or the power consumption of the motor being used as an indicator of the function of the servo device.
• Figure 1 shows a schematic perspective view of a steering arrangement for a vehicle according to the present invention
• Figure 2 shows a flow chart that describes the method for a vehicle with a steering arrangement according to the present invention
• Figure 3 shows the steering angle as a function of the number of rotations of the steering wheel, with the servo device working and a normal gear ratio, and with the servo device not working and thus with a high gear ratio, according to the present invention.
• FIG. 1 shows a schematic view of an example of a steering arrangement 1 for a heavy vehicle, for example in the form of a bus or a lorry.
• the steering arrangement 1 comprises a steering wheel 2 which is connected, via an upper steering column 3a, to a variable transmission 4 which, in turn, is connected, via a lower steering column 3b, to a steering gear 5 of the worm gear type where the lower part 6 of the steering column 3b is designed as a worm that is in engagement with a corresponding worm wheel on a steering shaft 7.
• An arm 8 is arranged on the steering shaft 7, which arm is, in turn, connected to a rod 10 arranged between the wheels 9 of the vehicle, which rod 10 transfers movements of the steering wheel ⁇ to movements of the wheels ⁇ via a drag link 11 and steering arms 12.
• a servo device 13 driven by the vehicle's propulsion motor (not shown), in the form of a hydraulic pump, is connected to the steering gear 5 via hydraulic pipes 14, 15.
• Control of the gear ratio in the variable transmission 4 is carried out by a central electronic control unit 16, hereafter called an ECU, which sends a signal to the said transmission 4 in response to the function of the said servo device 13, with the function, for example, being indicated by a pressure sensor for detecting the hydraulic pressure at the outlet of the hydraulic pump.
• Additional or alternative pressure sensors can also be arranged in other places in the hydraulic system in order, in this way, to give a good indication of the function of the servo device.
• an electrical for an electrical servo device for example the speed and/or the power consumption of the electric motor can be used as an indicator of the function of the servo device
• an electrical servo device for example the speed and/or the power consumption of the electric motor can be used as an indicator of the function of the servo device.
• FIG. 2 shows a schematic illustration of a flow chart that describes the method for the steering arrangement.
• the method starts Si when the driver starts S2 the vehicle.
• the ECU detects S3 the function of the servo device. If the servo device is not working, the ECU selects S4 a high gear ratio by sending a signal to the variable transmission whereupon this is controlled so that a high gear ratio is obtained.
• high gear ratio is meant here that the gear ratio is increased from a normal ratio by a factor in the range 1.2 to 3.5, preferably 1.25 to 2.25. If, however, the servo device is working, the ECU selects S5 a normal gear ratio in the said variable transmission.
• the ECU continually detects S6 the function of the servo device and maintains S7 the gear ratio as long as the servo device is working. If, for some reason, during operation, the servo device is no longer working, the ECU selects S4 a high gear ratio, as described above. Resetting of the gear ratio S8, after the servo device has not been working, is carried out after checks have been carried out in accordance with a predetermined routine. The method is thereby ended.
• Figure 3 shows examples of how the gear ratio affects the number of rotations of the steering wheel that are required between full lock positions .
• the lower line corresponds to a desired normal gear ratio where three rotations of the steering wheel are required between full lock positions, while the upper line shows a high gear ratio, in this case increased by a factor of two, which thus means that six rotations of the steering wheel are required in order to achieve the said movement between full lock positions.
• the gear ratio is varied in steps, this corresponds to lines (not shown) between the lines illustrated and when the gear ratio is varied steplessly, this corresponds to the area between the lines, that is to say the gear ratio can assume all values between the lines .
• a steering gear of the rack and pinion type can be used instead of the steering gear of the worm gear type described above.
• the variable transmission can be integrated in the said steering gear.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)
• Steering-Linkage Mechanisms And Four-Wheel Steering (AREA)
• Steering Controls (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=30768768

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (4)

Family Cites Families (17)

• 2003
  • 2003-12-17 SE SE0303449A patent/SE526240C2/sv not_active IP Right Cessation
• 2004
  • 2004-12-01 WO PCT/SE2004/001776 patent/WO2005058670A1/en not_active Application Discontinuation
  • 2004-12-01 DE DE602004021027T patent/DE602004021027D1/de active Active
  • 2004-12-01 AT AT04801699T patent/ATE430679T1/de not_active IP Right Cessation
  • 2004-12-01 EP EP04801699A patent/EP1697201B1/de not_active Not-in-force
• 2006
  • 2006-06-01 US US11/421,681 patent/US20060225947A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events